1. Field of the Invention
The present invention relates to an optical image reader making use of a diffraction effect by a hologram.
2. Description of the Related Art
An optical image reader which is generally and conventionally known as a flat head type operates on the basic principle of linearly reading an object image with an optical system primarily comprising an illuminator, a mirror, a lens, and a charge coupled device (CCD) line sensor. The optical image reader forms a two-dimensional image by successively repeating imaging of linear images and joining these linear images. The imaging is carried out while mechanically driving and unidirectionally moving a carriage of the optical system. (For example, refer to Japanese Unexamined Patent Application Publication Nos. 9-116703 and 2000-115455.) In order to move the carriage, such an optical image reader requires, for example, a motor for converting electrical energy into mechanical energy, a rail for supporting the carriage, and a shaft for converting rotational energy generated by the motor into a driving force in a unidimensional direction.
However, in the above-described optical image reader, the structure for mechanically moving the carriage is complicated. In addition, it is very difficult to downsize the optical image reader to a portable size.